Journal of Dental Research, Vol 66, 1380-1385, Copyright © 1987 by International & American Associations for Dental Research Online Journals
Adhesion of resins to Ag-Pd alloys by means of the silicoating technique
H. Hero, I. E. Ruyter, M. L. Waarli and G. Hultquist
The purpose of the investigation was to study the effect of water storage
on the bond strengths between silanized, silicoated Ag-Pd alloys and
veneered composites, in comparison with the bond strengths of systems with
conventional retention beads. Furthermore, the mechanism of the bonding was
examined. The bond strength of silanized, silicoated dry specimens and
similar specimens stored in water was measured by four-point bending. Water
storage for 90 days at 37 degrees C reduced the bond strength by
approximately 30% to about 15-20 MPa. Mechanical retention beads caused
bond strengths of approximately 16-18 MPa which were unaffected by water
storage. SEM and microprobe investigations showed that sandblasting with
AI2O3 prior to silanization caused substantial numbers of cracks and
porosities in the surface layer of the alloy, partly filled with Al2O3.
Some particles of silicon oxide in these surface defects were produced by
the flame-spraying of the so-called silicoating technique. Further painting
of the surface with a silane adhesion primer provided chemical bonding to
the composite at the densely spaced Si-O-H-containing silica particles.
Many cracks were observed in the interfaces between these particles; thus,
water is likely to penetrate the interface with time. The bond strength is
most likely reduced by reaction between water and the composite/Si-O
structure. The silicon oxide particles are probably attached to the alloy
substrate by mechanical retention. Without sandblasting, no bonding was
obtained by means of the silicoating technique.
